Screen

ABSTRACT

In a screen consisting of a supporting frame (1) which is covered with apertured (6) screen elements (2) of resilient material, said screen elements (2) are well supported and particularly easy to replace without intervention, e.g. by way of welding, as they have longitudinal guide grooves (7) which have a profile serving to be snapped on to the upper layer (3) of the supporting frame (1) and such a depth that the lower layer (4) of the supporting frame (1) engages the underside of the screen elements (2). In a preferred embodiment the wires or bars in the lower layer (4) of the supporting frame are disposed so as to be out of alignment with the apertures (6) of the screen elements so that also the wires in this layer are protected against wear.

BACKGROUND OF THE INVENTION

The invention relates to a screen consisting of a supporting frame onwhose upper side mutually adjoining, apertured screen elements ofresilient material with substantially rectangular borders are detachablyattached.

The apertured screen elements of resilient material are primarily toserve as wear-resistant screen means proper, but also have the task ofprotecting the supporting frame against the wear caused by the materialtreated by the screen.

However, the screen elements are nevertheless worn or otherwise damagedover an extending period of time, e.g. by falling screen material, andmust therefore be replaceable.

The Norwegian Published Application No. 142 943 discloses a screen ofthe type mentioned above, in which the replaceable screen elements areattached to the supporting frame by means of stud-shaped fasteners. Thistechnique is vitiated by the drawback that it requires the use of a verylarge number of fasteners, which can easily be lost and which can springup when the frame is deflected. Moreover, the fasteners are damaged moreor less when the screen elements are replaced.

Screens have been developed in which the fasteners are integral parts ofthe screen elements. However, this involves a very complicatedmanufacturing process which adds to the manufacturing costs of thescreen elements. The integral fasteners moreover break when theindividual screen elements are replaced. The resulting bottom framebecomes heavy, which reduces the vibration capacity of the machine.

The Federal Republic of Germany Utility Model No. 7 838 335 discloses afurther development of a screen where the screen elements are attachedby means of fasteners, which are firmly connected to a supportingstructure. These fasteners are rectilinear, specially made metalprofiles with an upwardly open U-shaped cross-section, whose free forksare extended at the top and lockingly engage longitudinal notches in theedges of their respective one of two adjoining screen elements. Thus,the screen elements are only supported at their longitudinal edges asthere is no supporting frame, and the load capacity of the screen istherefore not fully satisfactory.

Another known screen comprises a supporting frame of woven, speciallymade profile wires which are disposed perpendicularly to one another andto which rubber screen elements are attached, the screen elements beingprovided along all their edges with downwardly open grooves which can beclamped onto the wire net. The wire net cannot carry large loads withoutbeing deflected, and this construction is therefore not capable ofsupporting the screen elements to a satisfactory degree either. Therubber in the screen elements must moreover be so thin that it caneasily be replaced, but this significantly reduces the wear resistance.

OBJECTS OF THE INVENTION

The object of the invention is to form the screen elements so that,without the use of loose fasteners, they can be attached directly to andbe firmly supported by a very rigid and pressure resistant supportingframe, which is quite conventionally attached without any interventionin the machine by way of welding, and from which the screen elements areeasy to remove or mount in case of replacement. It is a further objectthat the screen is easy to adapt to various mesh sizes by replacing thescreen elements by others which have different aperture sizes, but fiton the same supporting frame, which can be conventionally replacedeasily and rapidly by a supporting frame of a different module.

SUMMARY OF THE INVENTION

These objects are achieved according to the invention by constructingthe screen defined in the foregoing so that the supporting frameconsists of an upper and a lower layer of substantially rectilinear,mutually parallel metal bars, the bars in the upper layer being disposedtransversely to the bars in the lower layer and joined with the bars ofsaid layer in the intersections, each screen element having at itsunderside at least two longitudinal guide grooves located outside thearea of the apertures, said guide grooves having a profile permittingsaid grooves to be snapped on to the upper layer of bars of thesupporting frame, said guide grooves having such a depth that the lowerlayer of bars of the supporting frame can engage the underside of thescreen elements. When the individual screen elements are to be replaced,they are just pulled upwards with a certain force in a directionperpendicular to the plane of the supporting frame so as to remove theclamping effect of a snap fastener nature between the guide grooves andthe upper layer of metal bars in the supporting frame. The new screenelements are then brought into place with the guide grooves just abovethe upper layer of metal bars and are snapped on by being presseddownwards. The overall screen or mesh area can be increased by 20 to 30%over the previous known constructions owing to the effective supportprovided by the frame.

The supporting frame may be a standard screen of the type which waspreviously used for screening purposes and which can be mounted on allknown screening machines without changing the frame of the machine orits set-up.

The screen elements themselves may have a mesh opening from 1 mm and upto 100-120 mm without any change of the supporting frame. The supportingframe for such a screen may easily be produced even under simplestmanufacturing conditions merely by inverting the screen elements andthen placing round bars in the guide grooves, where they may then beattached to form a net, which in turn is welded correctly together so asto form a rigid grid when the round bars have been removed from thescreen elements.

The manufactured screen elements are also advantageous in terms ofcasting. They can be made of plastics or rubber or another resilientmaterial, which may optionally be reinforced.

When the bars in the lower layer of the supporting frame are disposed soas to be out of alignment with the apertures of the screen elements,provision is made for support to the full extend of the bars in thelower layer of the supporting frame, and these bars are covered at thesame time and thus protected in their full extent by the screenelements.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be described more fully below with reference to thedrawing, which shows a perspective view of an embodiment of a screenaccording to the invention, seen obliquely from below.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The drawing shows a supporting frame 1 and two identical screen elements2, one of which is shown attached to the supporting frame 1, and otheris shown in a position vertically above the supporting frame 1.

The supporting frame 1 consists of a plurality of rectilinear, mutuallyparallel metal bars 3, which are disposed in an upper layer, and aplurality of likewise rectilinear, parallel metal bars 4, which aredisposed perpendicularly to the bars 3 of the upper layer and areattached to the underside of the upper metal bars 3, e.g. by welding, inthe intersections 5 of the wires 3,4. It will be noted that the bars 3of the upper layer and the bars 4 of the lower layer lie in only theirown layer. Bars 3 and 4 are generally uniform in shape.

The screen elements 2, which have rectangular borders, are provided withapertures 6 through which the material to be treated is passed. Thescreen elements have on their underside three guide grooves 7, which arenot aligned with the areas of the apertures 6 and have such a profilethat they can be snapped on to the upper layer of metal wires 3 in thesupporting frame.

The guide grooves 7 have such a depth that the lower layer of bars 4 ofthe supporting frame engages the underside of the screen elements 2 whenthe screen elements are attached to the supporting frame 1. Moreover,the metal bars 4 in the lower layer of the supporting frame 1 aredisposed so that they are out of alignment with the apertures 6 of thescreen elements 2.

In the shown embodiment the sides 8 and 9 of the guide grooves 7 extenddownwardly past the lowest layer of metal bars 4 and are thereforeprovided with recesses 10 at each intersection for the passage of themetal bars 4.

I claim:
 1. A screen which comprises a rigid supporting frame on whoseupper side mutually adjoining apertured screen elements of resilientmaterial with substantially rectangular borders are detachablysupported, said supporting frame consisting essentially of an upper anda lower layer of substantially rectilinear, mutually parallel metalbars, the bars of the respective layers lying essentially in only theirown layer, so that the bars of the upper layer lie only above the barsof the lower layer, the bars in the upper layer being disposedtransversely to the bars in the lower layer and joined with the bars ofsaid lower layer at intersections of said bars of said respective layerswhereby to form a rigid grid, each screen element having at itsunderside at least two longitudinal guide grooves located at bordersoutside the areas of the apertures, said guide grooves being constructedand arranged to be snapped onto the upper layer of bars, said guidegrooves having sufficient depth that the lower layer of the bars of thesupporting frame can engage the underside of the screen elements whenthe screen elements are supported by the upper layer, opposing sides ofthe guide grooves being provided with recesses for accomodating thepassage of the transversely extending bars of the lower layer.
 2. Ascreen according to claim 1, in which the bars in the lower layer of thesupporting frame are disposed so as to be out of alignment with theapertures of the screen elements.
 3. A screen according to claim 1, inwhich a plurality of apertures in the screen element lie within therectangular borders of said screen element.
 4. A screen according toclaim 1, in which the bars of both layers are substantially round.
 5. Ascreen according to claim 1, in which the bars of both layers aresubstantially uniform in shape.